Dual point circuit breaker having simplified spark advance mechanism



M. MALLORY 2,863,011 DUAL POINT CIRCUIT BREAKER HAVING SIMPLIFIED SPARKADVANCE MECHANISM Filed Aug. 28, 1957 United States Patent O DUAL POINTcnzcorr BREAKER HAVINGSIM- PLIFIED SPAR-K ADVANCE MECHANISM MarionMallory, Detroit, Mich., assignor to The Mallory Research Company,Detroit, Mich., a corporation of Michigan Application August 28, 1957,Serial N 0. 680,847

Claims. (Cl. 200-27) This invention relates to engine ignition systems,and particularly to dual point circuit breaker mechanisms employing tWosets of circuit breaker contacts, having overlapping closure periods.The invention is an improvement on the system and apparatus disclosed inU. S. Patent No. 1,663,207, issued March 20, 1928.

In the ordinary circuit breaker a single electrical switch both closesand opens the circuit. In the dual point ignition system there are twoelectrical switches, one closing the circuit and the other opening it.There is never any flashing in the contacts that close the circuitbecause they never open the circuit. Naturally there isnever-anycorrosion, scale or pitting in the contacts. that close the circuit andthe current always flows freely through the primary winding of the coil,saturating or magnetizing the coil core to its maximum. During the timeboth circuit breakers are closed there is, bound to be a free flow ofprimary current through the coil because the surface resistance of twosets of contacts is only one-half the surface resistance of one.Therefore, a good electrical circuit is always established.

With todays high compression eight cylinder engines it is very necessaryto have a hot, high voltage spark. To obtain this with a single circuitbreaker, the circuit breaker must be gapped closely, andwith present day12- volt electrical systems this causes excessive flashing of thecircuit breaker and short life. With dual circuit breakers, a widespacing can be used, still obtaining a long duration of coil saturationtime or dwell with no excessive flash- Objects of the present inventionare to provide an overlapping dual point ignition system wherein:

(1) Rotary timing advance plates and vacuum-piston type advancemechanisms are eliminated while still attaining desired spark advancefor better fuel economy at light engine loads.

(2) Spark advance is attained electrically rather than mechanically soas to reduce the time lag between change in engine load andcorresponding change in spark ad- Vance, the arrangement being such asto obtain increased fuel economy and freedom from advance plate stickingand failure of mechanical vacuum advance structures.

(3) At idle or low manifold vacuum when the engine is under heavy loadthe overlapping dual point principle is in operation, with the circuitbreaker which opens last doing the timing of the engine. When manifoldvacuum becomes high and the engine is under light load the circuitbreaker which opens last is disconnected through a vacuum-operatedelectric switch. This automatically causes the breaker which opens first(approximately eight degrees ahead of the breaker which opens last) tocontrol the timing of the engine, therefore automatically advancing theignition timing for light engine load and decreasing contact dwell orcoil saturation time; because only one breaker is in operation at lightengine loads the average breaker point temperature is decreased so as toincrease contact point life.

(4) The circuit breaker components may be constructed as relatively lowcost items by elimination of the relatively costly movable advance plateand vacuum piston type advance mechanism therefor.

Other objects of this invention will appear in the following descriptionand appended claims, referencetbeing had to the accompanying drawingsforming apart ofthis specification wherein like reference charactersdesignate corresponding parts inthe several views.

In the drawings, the single figure is a plan view of a distributorconstructed accordingto the present invention with its cap removed forillustration purposes, said distributor being shown in position of userelative to the spark coil, condenser, and vacuum-operated switch unitfor controlling the distributor action.

Before explaining the present invention in detail, it. is to, beunderstood that the invention is not limited, in its application to thedetails of construction and arrangement of parts illustrated in theaccompany drawings, since the invention is capable of other embodimentsand of. being practiced or carried out in various ways. Also, it is tobe understood that the phraseology or terminology employed herein isforthe purpose of description and not of limitation.

In the drawings there is shown an internal combustion engine ignitionsystem including a line 10 leading from the conventional ignition switch(not shown) to terminal 12 for the primary winding of a single inductionspark coil 14. The other primary winding terminal 16 is connectedthrough lines 18 and 19 to condenser 20 and circuit breaker terminal 22.

Terminal 22 is exteriorly insulated and projects through metallicdistributor housing 24 into electrical connection with a line 26.Housing 24 is provided with the conventional Bakelite cap (not shown)and rotor-segment structure for distributing secondary current from coil14 to the engine spark plugs. Secondary current is carried from the coilsecondary to the distributor cap via line 25.

Line 26 engages an insulating washer 27 located on ear 28 of a metallicmounting bracket 29. Bracket 29 is fixedly secured to a subjacentsupporting plate 30.by means of screws 31, said plate 30 being fixedlycarried by metallic casing 24.

A second insulating washer 32 is positioned against the other face ofear 28 so as to receive one end of a metallic leaf spring 33, theassembly of elements 33, 32,. 27 and 26 being supported on car 28 bymeans of a rivet 35. The other end of spring 33 is secured to a metalliccircuit breaker arm 36, which is mounted for pivotal movement on a pin37 carried by plate 30. Arm 36 includes a fibrous dielectric member 39and a metallic member 34. A pair of rivets 7 (only one of which isvisible) secure spring 33 onto the breaker arm and establish a currentpath between the spring and arm member 34.

Arm member 34 carries a contact point 40. Bracket 29 is provided with anupstanding car 41 which carries a registering point 42.

Opening and closing of points 40 and 42 is accomplished by means of theconventional distributor shaft 43 having a cam surface or lobe for eachof the engine cylinders, the illustrated shaft having eight lobes 44through 51 so as to be used with an eight cylinder engine. It will beappreciated that the number of lobes could be varied in accordance withthe number of engine cylinders since the invention is capable of usewith engines having any number of cylinders. During rotation of shaft 43cam surfaces 44 through 51 ride on extension 52 of arm 36, with spring33 biasing said arm toward the axis of shaft 43 so as to maintainextension 52 against the adjacent cam surface, the arrangement beingsuch that points 40 and 42 are opened and closed in accordance with therotated position of shaft 43.

A second set of contact points 40, 42' receives current from aninsulated terminal 54, which is connected with terminal 22 by means ofconductor 55. The mounting mechanism for points 40', 42 is similar tothat employed in conjunction with points 40, 42 and similar referencenumerals are therefore used.

Housing 24 carries a brackeet 57, which fixedly mounts a metal casing58. Casing 58 includes two cup-shaped sections 59 and 60, between whichis clamped a movable rubber diaphragm wall 61. A cylindricalforcetransmitting arm 62 is fixedly secured to diaphragm wall 61 andslidably extends through an opening in section 59 into a positionoverlying the breaker arm 36. The right end of arm 62 is turneddownwardly at 63 to freely engage the right face of arm 36. V

The end wall of section 60 is provided with an opening which mounts oneend of a vacuum line 64, the other end of said line being connected to afitting 85 screwed into the wall of a carburetor 66. Fitting 85communicates through opening 67 with the space just upstream fromthrottle valve 68, the arrangement being such that as the throttle valveis opened line 64 is put in communication with the engine inletmanifold. The vacuum within the manifold is thereby effective throughline 64 to move wall 61 to the left (to its illustrated position)against the action of spring 33. Spring 33 is so calibrated that nine toeleven inches of mercury manifold vacuum is required to move wall 61 tothe left (as illustrated) for moving contact 40 away from contact 42.Spring 33 may be replaced with a differently calibrated spring to obtaindifferent switchoperating vacuums.

Operation of the apparatus is such that when the manifold vacuum is lowswitch contacts 40 and 42 are closed so as to close the circuit throughconductor 26. Some of the spark coil primary current into terminal 22therefore flows through conductor 55 to terminal 54; the remaining sparkcoil primary current flows from terminal 22 through line 26, andeventually through points 40, 42 to plate 30 and out to ground. Thecurrent at terminal 54 flows through line 26, and eventually throughpoints 40', 42' to plate 30 and out to ground.

The mounting mechanisms for points 40, 42, 40' and 42' are so positionedthat points 40 and 42' close before points 40 and 42, as for example byabout eight shaft degrees. For approximately the next fifteen degreesboth sets of points are closed, for approximately the next eight degreesonly points 40, 42 are closed, and for the last fourteen degrees bothsets of points are open. This arrangement causes the primary coilcircuit to be closed by points 40', 42' and to be opened by points 40,42 with an overlapping period when both sets of points are closed. Thearrangement is advantageous by reason of minimum flashing, minimumcorrosion, minimum scale or pitting, and low point surface resistance,while increasing dwell time or coil saturation time to increase coilefficiency.

At cruising speeds under low load conditions fuel economy is enhanced byadvancing the spark from its position at high load conditions. Themanifold vacuum is increased at low load conditions so as to act throughdiaphragm 61 and arm 62 to open the circuit through contacts 40 and 42.As a result all of the current at terminal 22 must flow through points40', 42. Since these points open approximately eight degrees beforepoints 40, 42 the spark is automatically advanced by eight distributorshaft degrees or sixteen engine degrees, which is the most favorableadvance for enhanced fuel economy.

It will be noted that the change in spark advance is accomplished by adirect connection device between diaphragm 61 and breaker arm 39 ratherthan through a linkage system operating between a vacuum unit and rotaryadvance plate or other mechanical means. As a result the change in sparkadvance occurs almost instantaneously after change in manifold vacuumwith no time lag due to mechanical play of parts. Additionally allrotary support structure for the advance plate is eliminated so as toprovide a relatively simple low cost construction. A piston or othertype of pressure responsive movable wall structure can be employed inplace of diaphragm 61 if desired. With either the diaphragm constructionor the piston construction the mechanism can be constructed as arelatively low cost structure which gives trouble free performance overa long service life. It can be utilized both with distributors havingthe conventional centrifugal advance and with distributors not soequipped.

I claim:

1. In an ignition timing system for an internal combustion enginemechanism for interrupting spark coil primary current comprising a fixedsupport structure; first and second fixed contacts carried by saidsupport structure; first and second breaker arms movably carried on saidsupport structure; third and fourth contacts carried by the breaker armsin registry with respective ones of the first and second contacts;spring means urging the breaker arms to positions wherein the two setsof contacts are closed; a distributor shaft having cam surfaces engagedwith the breaker arms for sequentially opening the contacts; a fixedcasing having a movable wall; conduit means putting the interior of saidcasing in communication with engine intake vacuum to as to put themovable wall under control of the vacuum force; and an arm extendingfrom the movable wall to a releasable pressure connection with one ofthe breaker arms, whereby at high intake vacuum said one breaker arm isopen and at low intake vacuum said one breaker arm is positioned inaccordance with the rotated position of the distributor shaft, so as todecrease coil saturation time and increase timing at light engine load.

2. In an engine ignition system, mechanism for interrupting spark coilprimary current comprising a support structure; first and secondcontacts fixedly carried by said support structure; first and secondbreaker arms movably carried on said support structure; third and fourthcontacts carried by the breaker arms in registry wtih respective ones ofthe first and second contacts; spring means urging the breaker arms topositions wherein the two sets of contacts are closed; a distributorshaft having cam surfaces engaged with the breaker arms for sequentiallyopening the contacts; and means responsive to engine intake vacuum forholding one of the breaker arms away from the cam surfaces at highintake vacuum and allowing said one breaker arm to ride on the camsurfaces at low intake vacuum so as to decrease coil saturation time andincrease ignition timing at light engine load; said vacuum responsivemeans including a reciprocating arm engaging one of the breaker arms andsubject to the force of the vacuum.

3. In an ignition timing system for an internal combustion engine, anignition circuit including two circuit breakers in parallel and havingoverlapping closure periods, with one breaking later than the other butbefore the other again closes; said one circuit breaker including aswitch arm; wall means exposed to engine intake vacuum and movablethereby; and mechanically acting force-transmitting means between thewall means and switch arm for opening said one circuit breaker when theengine intake vacuum is above a predetermined value.

4. In an engine ignition timing system, mechanism for interrupting sparkcoil primary current comprising a fixed support structure; first andsecond contacts fixedly carried by said support structure; first andsecond breaker arms movably carried on said support structure; third andfourth contacts carried by the breaker arms in registry with respectiveones of the first and second contacts; spring means urging breaker armsto positions wherein the two sets of contacts are closed; a distributorshaft having cam surfaces engaged with the breaker arms for sequentiallyopening the contacts; a terminal for each set of contacts; conductormeans interconnecting said terminals; and means responsive to engineintake vacuum U for controlling the position of one of the breaker arms;said vacuum responsive means comprising a housing mounted on the fixedsupport structure and having a movable wall exposed to engine intakevacuum, and an arm extending from the movable wall and having an endportion hooked over said one breaker arm without interfering withmovement of said one breaker arm in a direction away from thedistributor shaft axis; whereby high engine intake vacuum draws themovable wall away from the distributor shaft axis so as to cause thewall-carried arm to pull said one breaker arm in a direction opposingthe action of its spring means for breaking the circuit through said onebreaker arm, while at low intake vacuum the spring means for said onebreaker arm is efiective to put said one breaker arm in continuousengagement with the cam surfaces.

5. In an ignition timing system for an internal combustion engine, anignition circuit including first and second circuit breakers in paralleland having overlapping closure periods, with the second breaking laterthan the first, but before the first again closes; one of said circuitbreakers including a switch arm; wall means exposed to engine intakevacuum and movable thereby; and mechanically acting force-transmittingmeans between the wall means and switch arm for opening said one circuitbreaker when the engine intake vacuum is above a predetermined value.

References Cited in he file of this patent UNITED STATES PATENTS

